1. Field of the Invention
The present invention relates to check valves, and more particularly but not by way of limitation, to a flow through check valve having improved flow characteristics and improved O-ring configuration.
2. History of the Prior Art
The prior art is replete with in-line check valves wherein a clapper member is pivotally mounted within the valve body and prevents flow in one direction by falling down into the flow stream and into contact with a valve seat also provided in the valve body.
It is desirable in many pipeline type uses that when the valve is in an open position, flow is completely unobstructed for the obvious purpose of preventing impedement of the flow of fluid therethrough and for the additional purpose of allowing a pipeline pig or other solid object to be passed through the pipeline and not be obstructed by the valve itself.
One such common check valve is taught in the patent to Wheatley, U.S. Pat. No. 2,918,934 issued Dec. 29, 1959 for a "Check Valve." Whereas the Wheatley valve included a recess near the access port to receive the valve clapper in the open position as shown in FIG. 1 thereof, it is seen that when the valve opened rapidly, which is often the case, the clapper would stop against the threaded portion of the access port cover thereby causing damage to the threads and often making removal of the access cover extremely difficult if not impossible.
In an attempt to solve this problem, many valve manufacturers then reduced the access opening causing the clapper to hit against the internal surface of the valve body rather than make contact with the access port cover. Often, since the valve body is enlarged to make room for the clapper, the volume of fluid through the valve was not impeded even though a portion of the clapper extended down into the flow stream. This provides no problem in allowing the passage of fluid through the valve but often presents a problem when a pig or other pipeline operation device is passed through the valve.
The typical valve clapper as taught in the patent to Wheatley is provided with a sealing member such as an O-ring around the upstream face thereof to provide a tight seal when the clapper is in place against the valve seat.
In order to prevent these O-rings from washing out of the clapper, the O-ring groove is made in the form of a dovetail annular groove so that the O-ring is literally stuffed inside the dovetail annular groove. It has been found that one of the primary causes for the washing out of the O-ring seal was that the clapper did not move fully up out of the flow stream after the valve had been modified to prevent the clapper from doing damage to the access cover. This particular dovetail annular groove for receiving the O-ring represents a great deal of manufacturing costs of the clapper and further gives rise to problems in installing the O-ring itself.